El estudio de los ecosistemas terrestres: problemas y perspectivas

Abstract

Theoretical development in terrestrial ecology found major difficulties in following the advances of aquatic ecology, particularly as a result of the relative terrestrial ecosystems staticism and complexity and heavier history weigh on them. Some concepts can not easily be applied, i.e, diversity has in them a better expression as structure richness and complexity than as specific variety; in any local succession, growth of biocenose-controlled volume and the transportways complexity are more relevant than the specific diversity increase but we do not have simple parameters quantifying these ideas. The r and K strategies constitute a not entirely satisfactory simplification, because a third one, stress resistance, seems almost so important. Plant demography development is far from that of animal demography, and this is a significant point as a result of plant dominancy in terrestrial ecology. So, descriptive aspects are overwhelming on dynamic and functional approaches, specially in the Mediterranean area, where edaphic and lithologic factors are sometimes so relevant as climate and where the heterogeneity is also increased - greatly by history. Heterogeneity make necessary a lot of inventory and description work and reduces data extrapolation possibilities. A lot of work has been made during the last 20 years in an intensive experimental plot approach in forest ecology, using highly sophisticated material for energy flows and nutrient cycling studies. Attention is born to vertical transport phenomena, but lateral flows are very important also in nature ecosystems as they are coupled with relief as an energetic subsidies way system. The functional divisibility of communities mosaic depends on this fact, and it makes obvious difficulties in driving experimental plot studies results to generalization. The relevancy of lateral flows has been enhanced in Spain by geobotanists as O. de Bolos or S. Rivas Martinez and plant ecologists as P. Montserrat, and the need for watershed ecosystems concept has clearly appeared. The most exhaustive study in a watershed optics is the Hubbard Brook ecosystems study, leadershipped by Bormann and Likens. We are now trying a mixed approach covering structural development process and vertical transport (demography, biomass, production, nutrients and water cycling, etc.) and, at the same time, the study of some lateral flows in the watershed and global in puts and outputs.